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Zero compression in one cylinder GL550. M273 engine
2008 GL550 with 223k miles. M273 engine.
Short story: very bad multiple/random misfires. Compression test showed ZERO psi for cylinder 5, while others got 170 psi.
Full story: a month ago engine shaking while idling but driving seems to be ok. was out of town so a week later engine won't start. so changed all spark plugs. one of the old spark plugs were in very bad shape. a small part of the ceramic near the tip was missing.
got error for crankshaft position sensor. got that changed (along with PCV valve). Engine runs ok, but got tapping sound. Indy shop said it's the lifters and gave me 300ml lifter additive and asked me to use 5w40 oil (used to be 0w40). So I changed the oil + additive. The tapping noise was gone. Everything was ok for 2 days. then all in a sudden the engine was shaking badly while driving. Pulled over and towed it home.
Not sure if revenant but I remembered I put too much oil + additive in. Probably 1 qt more. Very bad misfires, P0300, P0301, P0302, P0305, P0306 ... Not the same every time. Pumped out the oil, and even did another oil change. No improvement.
The engine would start, but shaking, then die after a few seconds. The spark plugs were wet -- not sure oil or gasoline. Cleaned them, swapped the coils. No improvement.
Use fuel injector cleaner (connect to the fuel rail + compressed air) and tried 3 different types of fluids (seafoam, Liqui Moly injector cleaner etc). No improvement.
Did a compression test, cylinder 5 has absolutely ZERO psi (the needle did not move at all), while 1, 2, 6, 7 got 170 psi (did not test the rest coz they didn't get a code and the battery was low).
*** Questions ***
1. possible that I did the compression wrong? (hope this is the case, but all the other cylinders i tested got good numbers)
2. if #5 is leaking so badly, what could the problem? Valve? I'm gonna do a leak down test after the storm in california.
3. saw some videos. looks like possible to remove the cylinder head by one person in his garage using normal hand tools. How difficult is this job really for a non professional mechanic? I did many little things (airbags, transfer case chain, transmission fluid change, fuel pump change, brake discs ...) on this car before but never opened up an engine.
4. or just get a used engine installed by an indy shop? what kind of bill to expect?
Its always possible that your test in No. 5 was wonky. Irrespective, there's a problem to sort and lots of potential items to consider. The best way to quickly work out if you have an engine that can be saved is to get a borescope into No. 5 and see if you have a piston and cylinder walls that are in shape and that it moves as it should by hand turning the crank. I'd avoid using the starter to avoid further damage.
As you have zero compression my mind goes to;
- Broken piston/con rod - unlikely with the M273 but still possible. Its a pretty well built engine.
- Zero compression is unlikely to be a broken piston ring. You'd still get some compression if it were.
- Valve stuck open - noting your discussion regarding your lifers its possible that one has moved from its position or is stuck leaving the valve open. Given you'd be having lifter noises for sometime, its more lklely to be a lifter issue than a broken valve (at least not initially).
If the cylinder borescope looks OK, I'd be pulling the valve cover to inspect the valve train looking for a loose or stuck valve and/or lifter.
Without knowing exactly the circumstances, did your shop recommend a leak down test or top end inspection when you visited?
Last edited by BlackML550; 02-05-2024 at 05:21 AM.
The cylinder misfire error codes are only determined by changes in engine speed - in other words, when a cylinder should be making torque, it doesn't, and the engine slows down. Thus when you get into bad shape, the error codes become erratic.
My guess is you have a sticking valve. If you are so inclined, get a good borescope with side view, and peek in the cylinders. I got one made by Teslong and it saved me when my engine was suffering carbon buildup on the intake valves. They aren't very expensive, under $200. But get a good one; the cheap ones will cause more frustration than they are worth.
It is possible that the sticking valve is due to deposits on the valve stem. I get that sometimes when I have been using cheap gas without fuel system cleaner; the engine struggles to start and shudders when cold. If it turns out to be a sticking valve, you can pull the intake manifold and spray carburetor cleaner on the back sides of the valves. Or pull the fuel injectors and spray through those ports.
You would want to be cautious about investing too much money in a motor with over 200K miles, of course.
If you go to access the intake, clean the top side very well. My motor had all sorts of grit there just waiting to fall in the cylinders..
I doubt you did the compression test wrong - it's pretty hard to mess that up. Plus, most likely you would have unscrewed the tester and re-screwed it back in to verify?
I doubt you have something broken - you most likely would have heard a horrible noise.
Boroscope, as mentioned, is the next step... primarily because you now get to buy a new tool! I bought one for about $40 on Amazon that hooks up wirelessly to my phone and I can monitor live or take pics/video with it. The video quality is amazingly good. Then the leak down as you were planning. Where the air leaks out will be the clue.
good info! thank you! I'll get the leak down test and borescope test done.
my shop just replaced the crankshaft position sensor for me, and gave me some lifter additive for the tapping noise. It was running fine back then. several days later i changed the oil (overfill) and got into this mess. car was towed back to my home. wanted to fix it myself.
the car would start, shaking wildly, then die after 3 seconds. If i rev up the engine to 3K rpm immediately after startup, it'll stay running. that's what i did when attempting to clean the fuel injectors a couple of days ago. I did hear a little metal clinking noise while the engine was running.
By the way, a quart of overfill should not cause major problems, certainly not the ones you are seeing. You also probably would see an oil pressure warning.
Overfill typically only becomes a problem when the rotating cranks splash in the oil and aerate it into a foam. When that foam starts getting sucked into the oil pump, you are running with low oil pressure because the foam compresses easily and then expands quickly out the passages after the oil pump. You basically get into low oil pressure. This would manifest in rod bearing failure. Along the way, you would see huge amounts of oil foam pushed up into the combustion chambers. It would be, to use a technical term, a real mess.
First order of business, I would absolutely get a borescope in there.
You could have a broken valve spring. That would result in the valve not closing all the way. The clearance between the lifter and the cam could be the clicking noise you hear.
Do not operate the motor further. The clicking noise you hear could also be the piston contacting the valve.
thank you! borescope and leak down tests are the next steps for me.
did carb cleaner fixed the carbon buildup problem in your engine?
A few days ago I used fuel injector cleaner, hooked up to the fuel rail directly and pressurized with compressed air. tried Seafoam, Berryman B-12 chemtool, and Liqui Moly fuel injector cleaner. Would these help clean up the carbon buildups as well?
got it. so no more compression testing, and borescope first thing after the storm. the car is parked outside.
Another thing i forgot to mention was: one of the old spark plugs were in very bad shape. part of the ceramic near the tip was missing.
No compression, damaged spark plug. Sorry mate, but if that spark plug came from cyl #5, that cylinder will have eaten a valve.
Double check with a borescope, but prepare for either an engine swap or repair. Repair would at least require the following:
- New piston.
- Remove cylinder head, get head repaired, skimmed, install new valve.
thank you! borescope and leak down tests are the next steps for me.
did carb cleaner fixed the carbon buildup problem in your engine?
A few days ago I used fuel injector cleaner, hooked up to the fuel rail directly and pressurized with compressed air. tried Seafoam, Berryman B-12 chemtool, and Liqui Moly fuel injector cleaner. Would these help clean up the carbon buildups as well?
Valve sticking tends to be due to varnish buildup on the valve stem. I bet the fuel injector cleaner took care of any varnish problem you have.
Carbon buildup would probably not be your problem. The carbon forms hot spots that lead to preignition, to the point the ECU goes out of bounds and quits.
You likely have a valve sticking open. Why is unknown; the most likely explanation I can think of is a broken valve spring, but why it would break only after 220K miles is hard to imagine. The other thing that could cause the valve to stick open is it getting bent, but that usually only happens if the engine valve timing goes off, such as with a broken timing belt. The valve timing system on these motors is very robust.
@Max Blast is talking about the e55 engine (the 5.5 liter M273 V8 used in the GL550 and many others), not the engine used in the E55.
Is it called the E55 engine or the M273 5.5L engine? Don't think I've ever heard of the M273 being referred to as the E55 engine. It was an evolution of the M113 used in the E55 though. Always looking to learn something new.
It would move it well and was used in the AMG G series in lieu of the 156 6.2L engine all the way until the bi-turbo M157 replaced it in 2013. Obviously, MB even thought it a better engine than the 156 to motivate the heavy G class.
m273 e47 = gl450 motor
m273 e55 = gl550
not to be confused with m113k = e55 motor
For those who did not quite follow the above:
M273 e47 = GL450 motor (4.7 liter displacement, hence the GL450 ought to be GL470 if MB marketing were at all technical but they are not, seemingly preferring form over function)
M273 e55 = GL550 (5.5 liter displacement)
M113 is the motor in the E55; the supercharged M113K ("Kompressor") was in the E55 ML.
The e47 motor was in just a few models; many more e55 motors were made. OP has a e55 motor so it is truly a drop-in.
still raining outside, but here's a pic of that spark plug. pretty scary. cannot remember if it's from cylinder 5 but very likely. hard to imagine what damage this piece of ceramic could do to the engine.
It’s likely in smaller pieces after being smashed by the exhaust valves, so look there first. If it’s not in the cylinder it’s likely stuck in the cat matrix.
It’s likely in smaller pieces after being smashed by the exhaust valves, so look there first. If it’s not in the cylinder it’s likely stuck in the cat matrix.
still playing w/ the borescope and leak down tester, but here are some preliminary results.
1. is this piston leaking oil? why its got some big "wrinkles" on the surface? anyways, it is probably not the root cause of 0 compression.
2. valve pics are not very clear. will try again tomorrow, but looks like they are not closed all the way down. tried to locate the TDC for three times. if connected to compressed air, one time air shot out from cylinder 1, another time it blew out from cylinder 6. not sure why. it seems nothing from coolant reservoir or oil filler cap or tail pipe.
3. unable to locate the porcelain pieces. it's quite difficult to maneuver the lens in there.
4. even if cylinder 5 is completely dead, isn't the engine supposed to idle with the rest 7 cylinders? why it shakes and dies after 3 seconds. Or this means other cylinders are bad too, as i got P0300 P030X codes?
02-05-2024, 01:11 AM
